In a multiple optical axis photoelectric sensor that detects an object in a two-dimensional detection area, a projector in which a plurality of light emitting elements are provided and an optical receiver in which as many light receiving elements as the light emitting elements are provided are aligned such that each projector light emitting element faces each a corresponding receiver light receiving element on a one-to-one basis. In the multiple optical axis photoelectric sensor, the process of detecting whether light emitted from the light emitting element of the validated optical axis enters the corresponding light receiving element (hereinafter referred to as “optical scan processing”), and process of determining whether the light obstruction of the optical axis is generated in the detection area based on the optical axis scan processing, are repeatedly performed. Further, a function of outputting a control signal for operating an external device is provided in the multiple optical axis photoelectric sensor that is used for the purpose of safety. The control signal is set to an on-state while a determination that the light is not obstructed in the detection area is made (hereinafter referred to as a “light entrance determination”). On the other hand, when light obstruction is determined in the detection area (hereinafter referred to as a “light obstruction determination”), the control signal is set to an off-state, namely, a control output is stopped (see Patent Document 1).
Patent Document 1 describes that, for quickening response speed while minimizing erroneous determinations caused by disturbance light, the light emitting element of the validated optical axis is emitted multiple times. Determination is made by capturing a light reception signal from the light receiving element in synchronization with timing corresponding to the light emission for each time interval. A signal indicating detection of an object is outputted when the light obstruction state is detected a predetermined number of times.